Key blank



United States Patent 3,385,697 KEY BLANK Peter Ii. Kabeika, Torrington,Conn, assignor to Anaconda American Brass Company, a corporation ofConnecticut No Drawing. Filed Nov. 9, 1964, Ser. No. 410,008 3 Claims.(Cl. 75-1575) ABSTRACT OF THE DISCLOSURE A key blank having the color,tarnish resistance, machinability and strength for good key formationhaving an alloy composition consisting of about the followingpercentages by weight: 58-61 percent copper, -15 percent manganese,0.51.5 percent lead and the remainder zinc.

This invention relates to key blanks, and more particularly it relatesto a key blank having a leaded coppermanganese-zinc alloy composition.

In the manufacture of key blanks careful consideration must be given tothe alloy composition for it is not only important that the key blankpossesses the desired properties for final formation into key form andsubsequent lasting use, but it also must be economically competitive.This determination of whether the alloy is economically competitiveinvolves an evaluation of the cost of production and the availability ofthe metals used in the alloy.

I have developed an alloy composition which is ideally suited for themanufacture of key blanks. The key blanks of the invention can be formedin a continuous series of operations from an initial continuous castingoperation and is formed of Only metals which are readily available andrelatively low in cost; and once formed into the key blank the alloyretains the necessary properties for ease of machining into the specifickey shape and the good edge retention properties to hold thecharacteristic irregular key edge formations.

Broadly stated the key blank is formed for machining into specific keyform and has an alloy composition consisting of about the followingpercentages by weight, about 58 to 61 percent copper, about 10-15percent mangnese, about 0.5 to 1.5 percent lead and the remainder zinc.It was specifically found that a key blank having essentially thefollowing percentages by weight, 59.5 percent copper, 12.5 percentmanganese, 1.0 percent lead and the remainder zinc, gives all therequired properties for good key formation and offers the economicaladvantages of being easy to mill and comprised of metals which arereadily available.

In one example, an alloy composition having 59.5 percent copper, 12.5percent manganese, 1.0 percent lead and the remainder zinc inpercentages by weight was melt- 3,385,097 Patented May 28, 1968 ed andcontinuously cast into bar form by one of the known continuous castingtechniques. The bar was successively hot and cold rolled withintermediate annealing to form a strip of about /2 inch thickness. Thestrip was finally reduced by cold reduction to a final strip size ofabout inch, which is one of many standard sized key blanks. The stripwas characterized by relatively fine grain size in the order of about0.065 mm. After final strip size was reached the strip was annealed at atemperature of 700 to 1500 F., it being found that at the higher annealing temperatures the tensile strength and hardness of the resultingkey blank was decreased and the percent elongation was correspondinglyincreased. Thus, this key blank alloy was found to be easily hot rolledand cold rolled and welded readily to give long coils for continuousstrip rolling. Moreover when ultimately stamped into key blank form thekey blank had the color, tarnish resistance, machinability and strengthrequired for good key formation.

It is to be noted that the copper-manganese-zinc alloys heretoforedeveloped, have never been used commercially because of the diflicultyin casting high manganese alloys which resulted in the formation of atough heavy skin of oxides which formed whenever the liquid alloy isexposed to air, as in pouring. By using a continuous casting techniqueso as to control the oxide skin formation, and varying the alloycomposition so as to provide good machinability of the resulting keyblank, the key blank formed is substantially free of oxide skin to theextent it is harmful and the key blank is easily machinable by known keymaking processes, usually filing.

I claim:

1. A key blank for machining into specific key form having an alloycomposition consisting of about the following percentages by weight, 58to 61 percent copper, 10 to 15 percent manganese, 0.5 to 1.5 percentlead and the remainder zinc.

2. A key blank for machining into specific key form having an alloycomposition consisting of about the following percentages by weight,59.5 percent copper, 12.5 percent manganese, 1.0 percent lead and theremainder zinc.

3. A key blank according to claim 2 having a grain size in the order ofabout 0.065 mm.

References Cited UNITED STATES PATENTS 2,347,706 5/1944 Moss -157.52,322,703 6/1947 Rodda 75157.5 2,479,596 8/1949 Anderson et al. 75157.52,772,962 12/1956 Reichenecker 75-157.5

DAVID L. RECK, Primary Examiner.

RICHARD O. DEAN, HYLAND BIZOT, Examiners.

